Magnetic random access memory

ABSTRACT

A data selection line (write line) is disposed right on a MTJ element. Upper and side surfaces of the data selection line are coated with yoke materials which have a high permeability. The yoke materials are separated from each other by a barrier layer. Similarly, a write word line is disposed right under the MTJ element. The lower and side surfaces of the write word line are also coated with the yoke materials which have the high permeability. The yoke materials on the lower and side surfaces of the write word line are also separated from each other by the barrier layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of and claims the benefit of priorityunder 35 USC §120 from U.S. Ser. No. 10/796,061, filed Mar. 10, 2004 nowU.S. Pat. No. 6,844,204, which is a division of Ser. No. 10/327,910filed on Dec. 26, 2002, now U.S. Pat. No. 6,737,691, issued May 18,2004, and is based upon and claims the benefit of priority under 35 USC§119 from the prior Japanese Patent Application No. 2002-301940, filedOct. 16, 2002, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic random access memory (MRAM)in which a MTJ (Magnetic Tunnel Junction) element for storing “1”,“0”-information by a TMR effect is used to constitute a memory cell.

2. Description of the Related Art

In recent years, a large number of memories in which information isstored by a new principle have been proposed. Among the memories, thereis a memory which uses a tunneling magneto resistive (hereinafterreferred to as TMR) effect proposed by Roy Scheuerlein et al. (refer toISSCC2000 Technical Digest p. 128 “A 10 ns Read and Write Non-VolatileMemory Array Using a Magnetic Tunnel Junction and FET Switch in eachCell”).

In a magnetic random access memory, a MTJ element stores “1”,“0”-information. As shown in FIG. 1, the MTJ element includes astructure in which an insulating layer (tunneling barrier) is held bytwo magnetic layers (ferromagnetic layers). The information to be storedin the MTJ element is judged by judging whether or not directions ofspin of two magnetic layers are parallel or anti-parallel.

Here, as shown in FIG. 2, “parallel” means that the directions of spinof two magnetic layers (direction of magnetization) are the same, and“anti-parallel” means that the directions of spin of two magnetic layersare opposite to each other (the directions of arrows indicate thedirections of spin).

It is to be noted that an anti-ferromagnetic layer is usually disposedin one of two magnetic layers. The anti-ferromagnetic layer is a memberfor fixing the spin direction of one magnetic layer and changing onlythe spin direction of the other magnetic layer to easily rewrite theinformation.

The magnetic layer whose spin direction is fixed is referred to as afixed or pinned layer. Moreover, the magnetic layer whose spin directioncan freely be changed in accordance with write data is referred to as afree or storage layer.

As shown in FIG. 2, when the spin directions of two magnetic layers areparallel to each other, tunnel resistance of the insulating layer(tunneling barrier) held between two magnetic layers is lowest. Thisstate is a “1”-state. Moreover, when the spin directions of two magneticlayers are anti-parallel, the tunnel resistance of the insulating layer(tunneling barrier) held between two magnetic layers is highest. Thisstate is a “0”-state.

A write operation principle with respect to the MTJ element will nextbriefly be described with reference to FIG. 3.

The MTJ element is disposed in an intersection of a write word line anddata selection line (read/write bit line) which intersect with eachother. Moreover, the write is achieved by passing a current into thewrite word line and data selection line, and using a magnetic fieldformed by the current flowing through both wires to set the spindirection of the MTJ element to be parallel or anti-parallel.

For example, when a magnetization easy axis of the MTJ element is anX-direction, the write word line extends in the X-direction, and thedata selection line extends in a Y-direction crossing at right angles tothe X-direction, a current directed in one direction is passed throughthe write word line at a write time, and a current directed in one orthe other direction is passed through the data selection line inaccordance with the write data.

When the current directed in one direction is passed through the dataselection line, the spin direction of the MTJ element becomes parallel(“1”-state). On the other hand, when the current directed in the otherdirection is passed through the data selection line, the spin directionof the MTJ element becomes anti-parallel (“0”-state).

A mechanism in which the spin direction of the MTJ element changes is asfollows.

When a magnetic field Hx is applied in a long-side (easy-axis) directionof the MTJ element as shown by a TMR curve of FIG. 4, the resistancevalue of the MTJ element changes, for example, by about 17%. This changeratio, that is, a ratio of the resistance values before and after thechange is referred to as an MR ratio.

It is to be noted that the MR ratio changes by properties of themagnetic layer. At present, the MTJ element whose MR ratio is about 50%is obtained.

A synthetic magnetic field of the magnetic field Hx of an easy-axisdirection and magnetic field Hy of a hard-axis direction is applied tothe MTJ element. As shown by a solid line of FIG. 5, the size of themagnetic field Hx of the easy-axis direction necessary for changing theresistance value of the MTJ element also changes by the size of themagnetic field Hy of the hard-axis direction. This phenomenon can beused to write data only into the MTJ element which exists in theintersection of the selected write word line and data selection lineamong memory cells arranged in an array form.

This state will further be described with reference to Astroid curve ofFIG. 5.

The Astroid curve of the MTJ element is shown, for example, by a solidline of FIG. 5. That is, when the size of the synthetic magnetic fieldof the magnetic field Hx of the easy-axis direction and the magneticfield Hy of the hard-axis direction is outside the Astroid curve (solidline) (e.g., in positions of black circles), the spin direction of themagnetic layer can be reversed.

Conversely, when the size of the synthetic magnetic field of themagnetic field Hx of the easy-axis direction and the magnetic field Hyof the hard-axis direction is inside the Astroid curve (solid line)(e.g., in positions of white circles), the spin direction of themagnetic layer cannot be reversed.

Therefore, when the sizes of the magnetic field Hx of the easy-axisdirection and the magnetic field Hy of the hard-axis direction arechanged, and the position of the size of the synthetic magnetic field inan Hx-Hy plane is changed, the write of the data with respect to the MTJelement can be controlled.

A read operation can easily be performed by passing a current throughthe selected MTJ element, and detecting the resistance value of the MTJelement.

For example, a switch element is connected in series to the MTJ element,and only the switch element connected to a selected read word line isturned on to form a current path. As a result, since the current flowsonly through the selected MTJ element, the data of the MTJ element canbe read out.

In the magnetic random access memory, as described above, the data writeis performed by passing the write current through the write word lineand data selection line (read/write bit line) and allowing a syntheticmagnetic field Hx+Hy generated thereby to act on the MTJ element.

Therefore, to efficiently perform the data write, it is important toefficiently apply the synthetic magnetic field Hx+Hy to the MTJ element.When the synthetic magnetic field Hx+Hy is efficiently applied to theMTJ element, reliability of the write operation is enhanced, further awrite current is reduced, and low power consumption can be realized.

However, an effective device structure for allowing the syntheticmagnetic field Hx+Hy generated by the write currents flowing through thewrite word line and data selection line to efficiently act on the MTJelement has not been sufficiently studied. That is, for the devicestructure, it naturally needs to be studied whether the syntheticmagnetic field Hx+Hy is actually efficiently applied to the MTJ element.Furthermore, in a manufacturing process aspect, it needs to be studiedwhether or not the structure can easily be manufactured.

In recent years, as a technique of efficiently applying the magneticfields Hx, Hy to the MTJ element, the device structure has been studiedin which a yoke material having a function of suppressing spread of themagnetic field is disposed around a write line (refer to U.S. Pat. No.6,174,737).

The yoke material has high permeability, and magnetic flux has aproperty of being concentrated on a material which has the highpermeability. Therefore, when the yoke material is used as a tractionmaterial of a magnetic force line, the magnetic fields Hx, Hy generatedby the write current flowing through the write line can efficiently beconcentrated on the MTJ element at a write operation time.

The yoke material has a function of suppressing the spread of themagnetic field as described above. This is based on a prerequisite thatfilm thickness and magnetic domain of the yoke material are accuratelycontrolled. That is, when dispersion is generated in the film thicknessof the yoke material arranged around the write line, and the magneticdomain is not orderly aligned, an effect of the yoke material inbunching a magnetic force line is reduced, and it becomes impossible toefficiently apply the magnetic fields Hx, Hy to the MTJ element.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, there is provided amagnetic random access memory comprising: a memory cell which uses amagneto resistive effect to store data; a first write line which isdisposed right on the memory cell and which extends in a firstdirection; a second write line which is disposed right under the memorycell and which extends in a second direction intersecting with the firstdirection; a first yoke material with which an upper surface of thefirst write line is coated; a second yoke material with which a sidesurface of the first write line is coated; and a first barrier layerwhich is disposed between the first yoke material and first write lineand between the second yoke material and first write line and whichseparates the first yoke material from the second yoke material.

According to another aspect of the present invention, there is provideda magnetic random access memory comprising: a memory cell which uses amagneto resistive effect to store data; a first write line which isdisposed right on the memory cell and which extends in a firstdirection; a second write line which is disposed right under the memorycell and which extends in a second direction intersecting with the firstdirection; a first yoke material with which a lower surface of thesecond write line is coated; a second yoke material with which a sidesurface of the second write line is coated; and a first barrier layerwhich is disposed between the first yoke material and first write lineand between the second yoke material and first write line and whichseparates the first yoke material from the second yoke material.

According to further aspect of the present invention, there is provideda manufacturing method of a magnetic random access memory, comprising: astep of forming a first yoke material on an insulating layer on asemiconductor substrate; a step of forming a conductive material on thefirst yoke material; a step of patterning the conductive material andfirst yoke material to form a write line whose lower surface is coatedwith the first yoke material; a step of forming a first barrier layerwith which the write line is coated; a step of forming a second yokematerial with which the write line is coated on the first barrier layer;a step of etching the first barrier layer and second yoke material toallow the first barrier layer and second yoke material to remain on theside surface of the write line; and a step of forming a memory cellwhich uses a magneto resistive effect to store data right on the firstwrite line.

According to still further aspect of the present invention, there isprovided a manufacturing method of a magnetic random access memory,comprising: a step of forming a memory cell which uses a magnetoresistive effect to store data on an insulating layer on a semiconductorsubstrate; a step of forming a conductive material right on the memorycell; a step of forming a first yoke material on the conductivematerial; a step of patterning the first yoke material and conductivematerial to form a write line whose upper surface is coated with thefirst yoke material; a step of forming a first barrier layer with whichthe write line is coated; a step of forming a second yoke material withwhich the write line is coated on the first barrier layer; and a step ofetching the first barrier layer and second yoke material to allow thefirst barrier layer and second yoke material to remain on the sidesurface of the write line.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagram showing a structure example of a MTJ element;

FIG. 2 is a diagram showing two states of the MTJ element;

FIG. 3 is a diagram showing a write operation principle of a magneticrandom access memory;

FIG. 4 is a diagram showing a TMR curve;

FIG. 5 is a diagram showing an Astroid curve;

FIG. 6 is a sectional view of the magnetic random access memoryaccording to a first reference example;

FIG. 7 is a sectional view of the magnetic random access memoryaccording to the first reference example;

FIG. 8 is a sectional view of the magnetic random access memoryaccording to a second reference example;

FIG. 9 is a sectional view of the magnetic random access memoryaccording to the second reference example;

FIG. 10 is a sectional view of the magnetic random access memoryaccording to a first embodiment;

FIG. 11 is a sectional view of the magnetic random access memoryaccording to the first embodiment;

FIG. 12 is a sectional view showing one step of a manufacturing methodof the memory according to the first embodiment;

FIG. 13 is a sectional view showing one step of the manufacturing methodof the memory according to the first embodiment;

FIG. 14 is a sectional view showing one step of the manufacturing methodof the memory according to the first embodiment;

FIG. 15 is a sectional view showing one step of the manufacturing methodof the memory according to the first embodiment;

FIG. 16 is a sectional view showing one step of the manufacturing methodof the memory according to the first embodiment;

FIG. 17 is a sectional view showing one step of the manufacturing methodof the memory according to the first embodiment;

FIG. 18 is a sectional view of the magnetic random access memoryaccording to a second embodiment;

FIG. 19 is a sectional view of the magnetic random access memoryaccording to the second embodiment;

FIG. 20 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 21 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 22 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 23 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 24 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 25 is a sectional view showing one step of the manufacturing methodof the memory according to the second embodiment;

FIG. 26 is a sectional view of the magnetic random access memoryaccording to a third embodiment;

FIG. 27 is a sectional view of the magnetic random access memoryaccording to the third embodiment;

FIG. 28 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 29 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 30 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 31 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 32 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 33 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 34 is a sectional view showing one step of the manufacturing methodof the memory according to the third embodiment;

FIG. 35 is a sectional view of the magnetic random access memoryaccording to a fourth embodiment;

FIG. 36 is a sectional view of the magnetic random access memoryaccording to the fourth embodiment;

FIG. 37 is a sectional view of the magnetic random access memoryaccording to a fifth embodiment;

FIG. 38 is a sectional view of the magnetic random access memoryaccording to a sixth embodiment; and

FIG. 39 is a sectional view of the magnetic random access memoryaccording to a seventh embodiment.

DETAILED DESCRIPTION OF THE INVENTION

A magnetic random access memory according to embodiments of the presentinvention will be described hereinafter in detail with reference to thedrawings.

1. FIRST REFERENCE EXAMPLE

A device structure as a prerequisite of the present invention will firstbe described before the magnetic random access memory according to anexample of the present invention.

It is to be noted that the device structure is described for ease ofunderstanding of the embodiment of the present invention, and thepresent invention is not limited to the device structure.

FIGS. 6 and 7 show the device structure as the prerequisite of theexample of the present invention.

Element separation insulating layers 12 including a shallow trenchisolation (STI) structure are formed in a semiconductor substrate (e.g.,a p-type silicon substrate, p-type well region, and the like) 11. Aregion surrounded with the element separation insulating layers 12 is anelement region in which a read selection switch (e.g., MOS transistor,diode, and the like) is formed.

In the device structure of FIG. 6, the read selection switch isconstituted of an MOS transistor (n-channel type MOS transistor). A gateinsulating layer 13, gate electrode 14, and side wall insulating layers15 are formed on the semiconductor substrate 11. The gate electrode 14extends in an X-direction, and functions as a read word line forselecting a read cell (MTJ element) at a read operation time.

A source region (e.g., n-type diffusion layer) 16-S and drain region(e.g., n-type diffusion layer) 16-D are formed in the semiconductorsubstrate 11. The gate electrode (read word line) 14 is disposed in achannel region between the source region 16-S and drain region 16-D.

In the device structure of FIG. 7, the read selection switch isconstituted of the diode. A cathode region (e.g., n-type diffusionlayer) 16 a and anode region (e.g., p-type diffusion layer) 16 b areformed in the semiconductor substrate 11.

One of metal layers constituting a first metal wiring layer functions asan intermediate layer 18A for vertically stacking a plurality of contactplugs, and another layer functions as a source line 18B (in FIG. 6) orread word line 18B (in FIG. 7).

In the device structure of FIG. 6, the intermediate layer 18A iselectrically connected to the drain region 16-D of the read selectionswitch (MOS transistor) by a contact plug 17A. The source line 18B iselectrically connected to the source region 16-S of the read selectionswitch via a contact plug 17B. The source line 18B extends in anX-direction similarly as the gate electrode (read word line) 14.

In the device structure of FIG. 7, the intermediate layer 18A iselectrically connected to the anode region 16 b of the read selectionswitch (diode) by the contact plug 17A. The read word line 18B iselectrically connected to the cathode region 16 a of the read selectionswitch via the contact plug 17B. The read word line 18B extends in theX-direction.

One of metal layers constituting a second metal wiring layer functionsas an intermediate layer 20A for vertically stacking a plurality ofcontact plugs, and another layer functions as a read word line 20B. Theintermediate layer 20A is electrically connected to the intermediatelayer 18A by a contact plug 19. The read word line 20B extends, forexample, in the X-direction.

One of metal layers constituting a third metal wiring layer functions asa lower electrode 22 of a MTJ element 23. The lower electrode 22 iselectrically connected to the intermediate layer 20A by a contact plug21. The MTJ element 23 is mounted on the lower electrode 22. Here, theMTJ element 23 is disposed right on the write word line 20B, and formedin a rectangular shape long in the X-direction (magnetization easy axisis the X-direction).

One of metal layers constituting a fourth metal wiring layer functionsas a data selection line (read/write bit line) 24. The data selectionline 24 is electrically connected to the MTJ element 23, and extends ina Y-direction.

It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of amulti-valued storage type in which data of a plurality of bits can bestored.

A ferromagnetic layer of the MTJ element 23 is not especially limited,and examples of a usable material include Fe, Co, Ni or an alloy ofthese metals, magnetite in spin polarization ratio, oxides such as CrO₂,RXMnO_(3-y) (R: rare earth metals, X: Ca, Ba, Sr), and Heusler alloyssuch as NiMnSb, PtMnSb.

Even with the ferromagnetic layer which contains some amount ofnonmagnetic elements such as Ag, Cu, Au, Al, Mg, Si, Bi, Ta, B, C, O, N,Pd, Pt, Zr, Ir, W, Mo, Nb, as long as ferromagnetism is not lost, thereis not any problem.

If the ferromagnetic layer becomes excessively thin, super-paramagnetismresults. To solve the problem, the ferromagnetic layer needs to have athickness to such an extent that at least the super-paramagnetism doesnot result. Concretely, the thickness of the ferromagnetic layer is setto 0.1 nm or more, preferably in a range of 0.4 nm to 100 nm.

As an anti-ferromagnetic layer of the MTJ element 23, for example,Fe—Mn, Pt—Mn, Pt—Cr—Mn, Ni—Mn, Ir—Mn, NiO, Fe₂O₃, and the like can beused.

As an insulating layer (tunneling barrier) of the MTJ element 23,dielectric materials such as Al₂O₃, SiO₂, MgO, AlN, Bi₂O₃, MgF₂, CaF₂,SrTiO₂, and AlLaO₃ can be used. Even when there is oxygen loss, nitrogenloss, or fluorine loss in these materials, there is no problem.

The thickness of the insulating layer (tunneling barrier) is preferablyas small as possible, but there is not especially a determinedlimitation for realizing the function. Additionally, the thickness ofthe insulating layer is set to 10 nm or less in a manufacturing process.

2. SECOND REFERENCE EXAMPLE

A device structure proposed with respect to the device structure of thefirst reference example in order to efficiently concentrate the magneticfield on the MTJ element will next be described.

FIGS. 8 and 9 show the device structure as the prerequisite of theexample of the present invention. It is to be noted that FIG. 8 shows asection of the Y-direction, and FIG. 9 shows a section of theX-direction of a MTJ element portion of FIG. 8. The X-direction crossesat right angles to the Y-direction.

The element separation insulating layers 12 including the STI structureare formed in the semiconductor substrate (e.g., the p-type siliconsubstrate, p-type well region, and the like) 11. The region surroundedwith the element separation insulating layers 12 is the element regionin which the read selection switch (e.g., MOS transistor) is formed.

In the device structure of the example, the read selection switch isconstituted of the MOS transistor (n-channel type MOS transistor). Thegate insulating layer 13, gate electrode 14, and side wall insulatinglayers 15 are formed on the semiconductor substrate 11. The gateelectrode 14 extends in the X-direction, and functions as the read wordline for selecting the read cell (MTJ element) at the read operationtime.

The source region (e.g., n-type diffusion layer) 16-S and drain region(e.g., n-type diffusion layer) 16-D are formed in the semiconductorsubstrate 11. The gate electrode (read word line) 14 is disposed on thechannel region between the source region 16-S and drain region 16-D.

One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

The intermediate layer 18A is electrically connected to the drain region16-D of the read selection switch (MOS transistor) by the contact plug17A. The source line 18B is electrically connected to the source region16-S of the read selection switch via the contact plug 17B. The sourceline 18B extends in the X-direction similarly as the gate electrode(read word line) 14.

One of the metal layers constituting the second metal wiring layerfunctions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

In the device structure of the present example, the lower and sidesurfaces of the intermediate layer 20A and write word line 20B arecoated with the material having the high permeability, that is, yokematerials 25A, 25B. The yoke materials 25A, 25B for use herein arelimited to the materials which have conductivity.

A magnetic flux has a property of being concentrated on the materialwhich has the high permeability. Therefore, when the material having thehigh permeability is used as a traction material of a magnetic forceline, a magnetic field Hy generated by a write current flowing throughthe write word line 20B can efficiently be concentrated on the MTJelement 23 at a write operation time.

The present object can sufficiently be achieved, when the lower and sidesurfaces of the write word line 20B are coated with the yoke material.Additionally, in actual, the yoke materials are formed on the lower andside surfaces of the intermediate layer 20A. This is because theintermediate layer 20A and write word line 20B are simultaneously formedas the second metal wiring layer.

One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

One of the metal layers constituting the fourth metal wiring layerfunctions as the data selection line (read/write bit line) 24. The dataselection line 24 is electrically connected to the MTJ element 23, andextends in the Y-direction.

In the device structure of the present example, the upper and sidesurfaces of the data selection line 24 are coated with the materialhaving the high permeability, that is, a yoke material 26. As shown inFIGS. 8 and 9, the yoke material 26 for use herein can be constituted ofa material which has conductivity, or may also be constituted of amaterial which has insulation property.

The yoke material 26 can be constituted of, for example, NiFe, CoFe,amorphous-CoZrNb, FeAlSi, FeNx, and the like.

As described above, the magnetic flux has the property of beingconcentrated on the material which has the high permeability. Therefore,when the material having the high permeability is used as the tractionmaterial of the magnetic force line, a magnetic field Hx generated bythe write current flowing through the data selection line 24 canefficiently be concentrated on the MTJ element 23 at the write operationtime.

It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of themulti-valued storage type in which data of a plurality of bits can bestored.

In this device structure, the yoke material 25B is formed on the lowerand side surfaces of the write word line 20B disposed right under theMTJ element 23. Moreover, the yoke material 26 is formed on the upperand side surfaces of the data selection line (read/write bit line) 24disposed right on the MTJ element 23.

However, in this case, the yoke material 25B around the write word line20B is also formed in a lower corner portion, and the yoke material 26around the data selection line 24 is also formed in an upper cornerportion.

For the yoke materials 25B, 26 of the corner portions of the write wordline 20B and data selection line 24, it is very difficult to control thefilm thickness in a manufacturing time (e.g., sputtering time), and thiscauses disorder in arrangement of magnetic domain of the yoke materials25B, 26. As a result, convergence effect of the magnetic field by theyoke materials 25B, 26 is reduced, and it becomes impossible toefficiently supply the magnetic field to the MTJ element.

3. FIRST EMBODIMENT

Embodiments of the present invention will next be described based on theabove-described first and second reference examples. The embodiment ofthe present invention relates to the device structure of the magneticrandom access memory in which the magnetic domain of the yoke materialdisposed around the write line can easily be controlled and the magneticfield can efficiently be concentrated on the MTJ element.

(1) Structure

FIGS. 10 and 11 show the device structure of the magnetic random accessmemory according to a first embodiment of the present invention. It isto be noted that FIG. 10 shows the section of the Y-direction, and FIG.11 shows the section of the X-direction of the MTJ element portion ofFIG. 10. The X-direction crosses at right angles to the Y-direction.

The device structure of the present embodiment is characterized in thatthe yoke material disposed on the lower or upper surface of the writeline is separated from the yoke material disposed on the side surface ofthe write line by a barrier layer and the yoke material extending to theside surface from the lower or upper surface is prevented from beingformed on the corner portion of the write line.

That is, the magnetic domain control of the yoke material disposed onthe lower or upper surface of the write line and the magnetic domaincontrol of the yoke material disposed on the side surface of the writeline are separately performed, thereby the magnetic domain control ofthe yoke material around the write line is facilitated, and theapplication efficiency of the magnetic field with respect to the MTJelement is enhanced.

The element separation insulating layers 12 including the STI structureare formed in the semiconductor substrate (e.g., the p-type siliconsubstrate, p-type well region, and the like) 11. The region surroundedwith the element separation insulating layers 12 is the element regionin which the read selection switch is formed.

The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

The source region (e.g., n-type diffusion layer) 16-S and drain region(e.g., n-type diffusion layer) 16-D are formed in the semiconductorsubstrate 11. The gate electrode (read word line) 14 is disposed on thechannel region between the source region 16-S and drain region 16-D.

One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

The intermediate layer 18A is electrically connected to the drain region16-D of the read selection switch (MOS transistor) by the contact plug17A. The source line 18B is electrically connected to the source region16-S of the read selection switch via the contact plug 17B. The sourceline 18B extends in the X-direction, for example, similarly as the gateelectrode (read word line) 14.

One of the metal layers constituting the second metal wiring layerfunctions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

The lower surfaces of the intermediate layer 20A and write word line 20Bare coated with the material having the high permeability, that is, yokematerials 25A1, 25B1. The yoke materials 25A1, 25B1 for use herein arelimited to the materials which have conductivity.

Barrier metals (e.g., Ti, TiN or a lamination of these) 27 a, 27 b areformed right under the yoke materials 25A1, 25B1, and barrier metals(e.g., Ti, TiN or the lamination of these) 27 c, 27 d are formed righton the barrier metals. That is, the yoke materials 25A1, 25B1 are heldbetween the barrier metals 27 a, 27 b, 27 c, 27 d.

The barrier metals 27 a, 27 b, 27 c, 27 d prevent atoms constituting theyoke materials 25A1, 25B1 from being diffused.

Moreover, the side surfaces of the intermediate layer 20A and read wordline 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2. Here, the yokematerials 25A2, 25B2 for use herein may have either conductivity orinsulation property.

When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as the tractionmaterial of the magnetic force line, the magnetic field Hy generated bythe write current flowing through the write word line 20B canefficiently be concentrated on the MTJ element 23.

Barrier layers 28 a, 28 b (e.g., Ti, TiN or the lamination of these, orTa, TaN or the lamination of these) are formed on the side surfaces ofthe intermediate layer 20A and write word line 20B. The barrier layers28 a, 28 b separate the yoke materials 25A1, 25B1 with which the lowersurfaces of the intermediate layer 20A and write word line 20B arecoated from the yoke materials 25A2, 25B2 with which the side surfacesare coated.

The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b. In thiscase, since the barrier layers 28 a, 28 b sufficiently fulfill adiffusion prevention function of atoms, each of the layers preferablyhas a thickness of at least about 20 nm.

One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

One of the metal layers constituting the fourth metal wiring layerfunctions as the data selection line (read/write bit line) 24. The dataselection line 24 is electrically connected to the MTJ element 23, andextends in the Y-direction.

The upper surface of the data selection line 24 is coated with thematerial having the high permeability, that is, the yoke material 26.The yoke material 26 for use herein may have either conductivity orinsulation property.

A barrier metal (e.g., Ti, TiN or the lamination of these) 29 forpreventing the atoms from being diffused is formed on the lower surfaceof the data selection line 24, and a barrier layer (e.g., Ti, TiN or thelamination of these, or Ta, TaN or the lamination of these) 30 is formedon the upper surface of the data selection line.

Moreover, the side surface of the data selection line 24 is also coatedwith the material which has the high permeability, that is, yokematerials 32. The yoke material 32 for use herein may have eitherconductivity or insulation property.

When the yoke materials 26, 32 are used as the traction material of themagnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

Barrier layers 31 (e.g., Ti, TiN or the lamination of these, or Ta, TaNor the lamination of these) are formed on the side surfaces of the dataselection line 24. The barrier layers 31 separate the yoke material 26with which the upper surface of the data selection line 24 is coatedfrom the yoke materials 32 with which the side surfaces of the dataselection line are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29. Since the barrier layers 30,31 sufficiently fulfill the diffusion prevention function of atoms, eachof the layers preferably has a thickness of at least about 20 nm.

It is to be noted that the structure of the MTJ element 23 is notespecially limited. The structure may be the structure shown in FIG. 1or any other structure. Moreover, the MTJ element 23 may also be of themulti-valued storage type in which data of a plurality of bits can bestored.

(2) Manufacturing Method

A manufacturing method of the magnetic random access memory according tothe first embodiment of the present invention will next be described.

First, as shown in FIG. 12, known methods such as a photo engravingprocess (PEP) method, chemical vapour deposition (CVD) method, andchemical mechanical polishing (CMP) process are used to form the elementseparation insulating layer 12 including the STI structure in thesemiconductor substrate 11.

Moreover, the MOS transistor as the read selection switch is formed inthe element region surrounded with the element separation insulatinglayer 12.

After forming the gate insulating layer 13 and gate electrode (read wordline) 14 by CVD method, PEP method, and reactive ion etching (RIE)method, the source region 16-S and drain region 16-D are formed by anion implantation method, so that the MOS transistor can easily beformed. It is to be noted that the side wall insulating layers 15 mayalso be formed on side wall portions of the gate electrode 14 by the CVDand RIE methods.

Thereafter, an insulating layer 28A with which the MOS transistor iscompletely coated is formed by the CVD method. Moreover, the surface ofthe insulating layer 28A is flatted using the CMP method. Contact holesreaching the source region 16-S and drain region 16-D of the MOStransistor are formed in the insulating layer 28A using the PEP and RIEmethods.

Barrier metals (e.g., Ti, TiN, or the lamination of these) 51 are formedon the insulating layer 28A and on the inner surfaces of the contactholes by a sputter method. Subsequently, conductive materials (e.g., aconductive polysilicon film including impurities, metal film, and thelike) with which the contact holes are completely filled are formed onthe insulating layer 28A by the sputter method. Moreover, by the CMPmethod, the conductive materials and barrier metals 51 are polished, andthe contact plugs 17A, 17B are formed.

An insulating layer 28B is formed on the insulating layer 28A using theCVD method. The PEP and RIE methods are used to form wiring trenches inthe insulating layer 28B. The sputter method is used to form barriermetals (e.g., Ti, TiN, or the lamination of these) 52 on the insulatinglayer 28B and on the inner surfaces of the wiring trenches.Subsequently, the conductive materials (e.g., metal films such asaluminum and copper) with which the wiring trenches are completelyfilled are formed on the insulating layer 28B by the sputter method.Thereafter, by the CMP method, the conductive materials and barriermetals 52 are polished, and the intermediate layer 18A and source line18B are formed.

Subsequently, the CVD method is used to form an insulating layer 28C onthe insulating layer 28B. The PEP and RIE methods are used to form viaholes in the insulating layer 28C. By the sputter method, barrier metals(e.g., Ti, TiN, or the lamination of these) 53 are formed on theinsulating layer 28C and on the inner surfaces of the via holes.Subsequently, by the sputter method, the conductive materials (e.g., themetal films such as aluminum and copper) with which the via holes arecompletely filled are formed on the insulating layer 28C. Thereafter, bythe CMP method, the conductive materials and barrier metals 53 arepolished, and a via plug 19 is formed.

Subsequently, as shown in FIG. 13, by the sputter method, the barriermetals (e.g., a lamination of Ti (10 nm) and TiN (10 nm)) 27 a, 27 b areformed on the insulating layer 28C. Subsequently, the sputter method isused to form the yoke materials (e.g., NiFe) 25A1, 25B1 which have thehigh permeability in a thickness of about 50 nm on the barrier metals 27a, 27 b. Moreover, the sputter method is used to form barrier metals(e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27 c, 27 d on theyoke materials 25A1, 25B1.

Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Thereafter, the PEP and RIE methods are usedto etch the conductive materials, yoke materials 25A1, 25B1, and barriermetals 27 a, 27 b, 27 c, 27 d, so that the intermediate layer 20A andwrite word line 20B are formed.

Additionally, the sputter method is used to form the barrier layers(e.g., a lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 b with whichthe intermediate layer 20A and write word line 20B are coated. Thesputter method is continuously used to form the yoke materials (e.g.,NiFe) 25A2, 25B2 which have the high permeability in a thickness ofabout 50 nm on the barrier layers 28 a, 28 b.

Moreover, by the RIE method, the yoke materials 25A2, 25B2 and barrierlayers 28 a, 28 b are etched, so that the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b remain only on the side wall portions of theintermediate layer 20A and write word line 20B.

Thereafter, the CVD method is used to form an insulating layer 29A withwhich the intermediate layer 20A and write word line 20B are completelycoated on the insulating layer 28C. Moreover, the surface of theinsulating layer 29A is flatted, for example, by the CMP method.

Subsequently, as shown in FIG. 14, the PEP and RIE methods are used toform the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, barrier metals (e.g., Ti,TiN, or the lamination of these) 55 are formed on the insulating layer29A and on the inner surfaces of the via holes in a thickness of about10 nm. Subsequently, the conductive materials (e.g., the metal film suchas tungsten) with which the via holes are completely filled are formedon the insulating layer 29A by the CVD method. Thereafter, by the CMPmethod, the conductive materials and barrier metals 55 are polished, anda via plug 21 is formed.

The CVD method is used to form an insulating layer 30A on the insulatinglayer 29A. The PEP and RIE methods are used to form the wiring trenchesin the insulating layer 30A. By the sputter method, the conductivematerials (e.g., the metal films such as Ta) with which the wiringtrenches are completely filled are formed on the insulating layer 30A ina thickness of about 30 nm. Thereafter, by the CMP, the conductivematerials are polished, and a local interconnect line (lower electrodeof the MTJ element) 22 is formed.

The CVD method is used to successively deposit a plurality of layers onthe local interconnect line 22, and these plurality of layers arefurther patterned to form the MTJ elements 23.

The MTJ element 23 is constituted of a lamination film including, forexample, Ta (about 40 nm), NiFe (about 10 nm), Al₂O₃ (about 2 nm), CoFe(about 10 nm), and IrMn (about 10 nm), or a lamination film includingNiFe (about 5 nm), IrMn (about 12 nm), CoFe (about 3 nm), AlOx (about1.2 nm), CoFe (about 5 nm), and NiFe (about 15 nm).

Moreover, the CVD method is used to form an insulating layer 30B withwhich the MTJ element 23 is coated, and subsequently, the insulatinglayer 30B on the MTJ element 23 is removed, for example, by the CMPmethod. As a result, a topmost layer of the MTJ element 23 is exposed,and only the side surface of the MTJ element 23 is coated with theinsulating layer 30B.

It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

Subsequently, as shown in FIG. 15, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

Furthermore, the yoke material (such as NiFe) 26 which has the highpermeability is continuously formed in a thickness of about 50 nm on thebarrier layer 30 by the sputter method. Thereafter, the PEP method isused to form a resist pattern 33.

Additionally, the RIE method is used, and the resist pattern 33 is usedas a mask to etch the yoke material 26, barrier layer 30, conductivematerial, and barrier metal 29, so that the data selection line(read/write bit line) 24 is formed.

Thereafter, the resist pattern 33 is removed.

Subsequently, as shown in FIG. 16, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

Moreover, when the yoke material 32 and barrier layer 31 are etched bythe RIE method, as shown in FIG. 17, the yoke material 32 and barrierlayer 31 remain only on the side wall portion of the data selection line24.

The magnetic random access memory of the first embodiment (FIGS. 10 and11) is completed by the above-described steps.

(3) Conclusion

As described above, according to the first embodiment, the lower surfaceof the write word line 20B is coated with the yoke material 25B1, andthe side surface of the line is coated with the yoke material 25B2.Moreover, since the yoke materials 25B1, 25B2 are separated from eachother by the barrier layer 28 b, the yoke material covering the lowerand side surfaces of the write word line is not formed in the lowercorner portion of the write word line 20B.

Therefore, the magnetic domains of the yoke materials 25B1, 25B2 areeasily controlled, and the magnetic field Hy generated by the writecurrent flowing through the write word line 20B can efficiently beexerted onto the MTJ element 23.

Moreover, according to the first embodiment, the upper surface of thedata selection line 24 is coated with the yoke material 26, and the sidesurface of the data selection line is coated with the yoke material 32.Furthermore, since the yoke materials 26, 32 are separated from eachother by the barrier layer 31, the yoke material covering the upper andside surfaces of the data selection line is not formed in the uppercorner portion of the data selection line 24.

Therefore, the magnetic domains of the yoke materials 26, 32 are easilycontrolled, and the magnetic field Hx generated by the write currentflowing through the data selection line 24 can efficiently be exertedonto the MTJ element 23.

4. SECOND EMBODIMENT

FIGS. 18 and 19 show the device structure of the magnetic random accessmemory according to a second embodiment of the present invention. It isto be noted that FIG. 18 shows the section of the Y-direction, and FIG.19 shows the section of the X-direction of the MTJ element portion ofFIG. 18. The X-direction crosses at right angles to the Y-direction.

The device structure of the present embodiment is characterized in thatthe yoke material covering the lower and side surfaces of the write lineis coated with the barrier layer having a function of preventing thediffusion of the atoms and the yoke material covering the upper and sidesurfaces of the data selection line is further coated with the barrierlayer having the function of preventing the diffusion of atoms.

The element separation insulating layers 12 including the STI structureare formed in the semiconductor substrate (such as the p-type siliconsubstrate and p-type well region) 11. The region surrounded with theelement separation insulating layers 12 is the element region in whichthe read selection switch is formed.

The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

The source region (e.g., n-type diffusion layer) 16-S and drain region(e.g., n-type diffusion layer) 16-D are formed in the semiconductorsubstrate 11. The gate electrode (read word line) 14 is disposed on thechannel region between the source region 16-S and drain region 16-D.

One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

The intermediate layer 18A is electrically connected to the drain region16-D of the read selection switch (MOS transistor) by the contact plug17A. The source line 18B is electrically connected to the source region16-S of the read selection switch via the contact plug 17B. The sourceline 18B extends in the X-direction, for example, similarly as the gateelectrode (read word line) 14.

One of the metal layers constituting the second metal wiring layerfunctions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

The lower surfaces of the intermediate layer 20A and write word line 20Bare coated with the material having the high permeability, that is, yokematerials 25A1, 25B1.

The barrier metals (e.g., Ti, TiN, or the lamination of these) 27 a, 27b are formed right under the yoke materials 25A1, 25B1, and the barriermetals (e.g., Ti, TiN, or the lamination of these) 27 c, 27 d are formedright on the barrier metals. That is, the yoke materials 25A1, 25B1 areheld between the barrier metals 27 a, 27 b, 27 c, 27 d.

Moreover, the side surfaces of the intermediate layer 20A and write wordline 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2.

When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as the tractionmaterial of the magnetic force line, the magnetic field Hy generated bythe write current flowing through the write word line 20B canefficiently be concentrated on the MTJ element 23.

The barrier layers 28 a, 28 b (e.g., Ti, TiN, or the lamination ofthese, or Ta, TaN, or the lamination of these) are formed on the sidesurfaces of the intermediate layer 20A and write word line 20B. Thebarrier layers 28 a, 28 b separate the yoke materials 25A1, 25B1 withwhich the lower surfaces of the intermediate layer 20A and write wordline 20B are coated from the yoke materials 25A2, 25B2 with which theside surfaces are coated.

The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b.

Additionally, when the atoms of the materials constituting the yokematerials 25A1, 25B1, 25A2, 25B2 reach the semiconductor substrate 11 bythe diffusion, the characteristics of the read selection switch (MOStransistor) formed on the surface region of the semiconductor substrate11 are sometimes adversely affected.

To solve the problem, in the second embodiment, the yoke materials 25A1,25B1, 25A2, 25B2 are coated with the barrier layer (such as SiN) 34which has the function of preventing the diffusion of atoms. Thereby,the diffusion of the atoms of the materials constituting the yokematerials 25A1, 25B1, 25A2, 25B2 is suppressed.

It is to be noted that the barrier layer 34 is constituted of aninsulating material. Additionally, the barrier layer 34 may also beconstituted of the conductive material, if the problem of short-circuitbetween the wires disposed adjacent to each other can be solved.

One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

One of the metal layers constituting the fourth metal wiring layerfunctions as the data selection line (read/write bit line) 24. The dataselection line 24 is electrically connected to the MTJ element 23, andextends in the Y-direction.

The upper surface of the data selection line 24 is coated with thematerial having the high permeability, that is, the yoke material 26.The barrier metal (e.g., Ti, TiN, or the lamination of these) 29 isformed on the lower surface of the data selection line 24, and thebarrier layer (e.g., Ti, TiN, or the lamination of these, or Ta, TaN, orthe lamination of these) 30 is formed on the upper surface of the dataselection line.

Moreover, the side surface of the data selection line 24 is also coatedwith the material which has the high permeability, that is, the yokematerials 32.

When the yoke materials 26, 32 are used as the traction material of themagnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

The barrier layers 31 (e.g., Ti, TiN, or the lamination of these, or Ta,TaN, or the lamination of these) are formed on the side surfaces of thedata selection line 24. The barrier layers 31 separate the yoke material26 with which the upper surface of the data selection line 24 is coatedfrom the yoke materials 32 with which the side surfaces of the dataselection line are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29.

Also with respect to the yoke materials 26, 32, similarly as the yokematerials 25A1, 25B1, 25A2, 25B2 with which the write word line 20B iscoated, when the atoms of the materials constituting the yoke materialsreach the semiconductor substrate 11 by the diffusion, thecharacteristics of the read selection switch (MOS transistor) formed inthe surface region of the semiconductor substrate 11 are sometimesadversely affected.

To solve the problem, the yoke materials 26, 32 are coated with barrierlayer (such as SiN) 35 which has the function of preventing thediffusion of atoms. Thereby, the diffusion of the atoms of the materialsconstituting the yoke materials 26, 32 is suppressed.

It is to be noted that the barrier layer 35 is constituted of theinsulating material. Additionally, the barrier layer 35 may also beconstituted of the conductive material, if the problem of short-circuitbetween the wires disposed adjacent to each other can be solved.

(2) Manufacturing Method

The manufacturing method of the magnetic random access memory accordingto the second embodiment of the present invention will next bedescribed.

First, as shown in FIG. 20, the methods such as the PEP, CVD, and CMPmethods are used to form the element separation insulating layer 12including the STI structure in the semiconductor substrate 11.

Moreover, the MOS transistor as the read selection switch is formed inthe element region surrounded with the element separation insulatinglayer 12.

After forming the gate insulating layer 13 and gate electrode (read wordline) 14 by the CVD, PEP, and RIE methods, the source region 16-S anddrain region 16-D are formed by an ion implantation method, so that theMOS transistor can easily be formed. The side wall insulating layers 15may also be formed on side wall portions of the gate electrode 14 by theCVD and RIE methods.

Thereafter, the insulating layer 28A with which the MOS transistor iscompletely coated is formed by the CVD method. Moreover, the surface ofthe insulating layer 28A is flatted using the CMP method. The contactholes reaching the source region 16-S and drain region 16-D of the MOStransistor are formed in the insulating layer 28A using the PEP and RIEmethods.

The barrier metals (e.g., Ti, TiN, or the lamination of these) 51 areformed on the insulating layer 28A and on the inner surfaces of thecontact holes by the sputter method. Continuously, the conductivematerials (e.g., the conductive polysilicon film including theimpurities, metal film, and the like) with which the contact holes arecompletely filled are formed on the insulating layer 28A by the sputtermethod. Moreover, by the CMP method, the conductive materials andbarrier metals 51 are polished, and the contact plugs 17A, 17B areformed.

The insulating layer 28B is formed on the insulating layer 28A using theCVD method. The PEP and RIE methods are used to form the wiring trenchesin the insulating layer 28B. The sputter method is used to form thebarrier metals (e.g., Ti, TiN, or the lamination of these) 52 on theinsulating layer 28B and on the inner surfaces of the wiring trenches.Continuously, the conductive materials (e.g., the metal films such asaluminum and copper) with which the wiring trenches are completelyfilled are formed on the insulating layer 28B by the sputter method.Thereafter, by the CMP, the conductive materials and barrier metals 52are polished, and the intermediate layer 18A and source line 18B areformed.

Subsequently, the CVD method is used to form the insulating layer 28C onthe insulating layer 28B. The PEP and RIE methods are used to form thevia holes in the insulating layer 28C. By the sputter method, thebarrier metals (e.g., Ti, TiN, or the lamination of these) 53 are formedon the insulating layer 28C and on the inner surfaces of the via holes.Continuously, by the sputter method, the conductive materials (e.g., themetal films such as aluminum and copper) with which the via holes arecompletely filled are formed on the insulating layer 28C. Thereafter, bythe CMP method, the conductive materials and barrier metals 53 arepolished, and the via plug 19 is formed.

Subsequently, as shown in FIG. 21, by the sputter method, the barriermetals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27 a, 27 bare formed on the insulating layer 28C. Subsequently, the sputter methodis used to form the yoke materials (e.g., NiFe) 25A1, 25B1 which havethe high permeability in a thickness of about 50 nm on the barriermetals 27 a, 27 b. Moreover, the sputter method is used to form thebarrier metals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27c, 27 d on the yoke materials 25A1, 25B1.

Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Thereafter, the PEP and RIE methods are usedto etch the conductive materials, yoke materials 25A1, 25B1, and barriermetals 27 a, 27 b, 27 c, 27 d, so that the intermediate layer 20A andwrite word line 20B are formed.

Additionally, the sputter method is used to form the barrier layers(e.g., the lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 b withwhich the intermediate layer 20A and write word line 20B are coated. Thesputter method is continuously used to form the yoke materials (e.g.,NiFe) 25A2, 25B2 which have the high permeability in a thickness ofabout 50 nm on the barrier layers 28 a, 28 b.

Moreover, by the RIE method, the yoke materials 25A2, 25B2 and barrierlayers 28 a, 28 b are etched, so that the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b remain only on the side wall portions of theintermediate layer 20A and write word line 20B.

Thereafter, the CVD method is used to form the barrier layer (such asSiN) 34 with which the yoke materials 25A1, 25B1, 25A2, 25B2 are coatedin a thickness of about 20 nm. The CVD method is continuously used toform the insulating layer 29A with which the intermediate layer 20A andwrite word line 20B are completely coated on the barrier layer 34.Moreover, for example, by the CMP method, the surface of the insulatinglayer 29A is flatted.

Subsequently, as shown in FIG. 22, the PEP and RIE methods are used toform the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, the barrier metals (e.g.,Ti, TiN, or the lamination of these) 55 are formed on the insulatinglayer 29A and on the inner surfaces of the via holes in a thickness ofabout 10 nm. Continuously, the conductive materials (e.g., the metalfilm such as tungsten) with which the via holes are completely filledare formed on the insulating layer 29A by the CVD method. Thereafter, bythe CMP method, the conductive materials and barrier metals 55 arepolished, and the via plug 21 is formed.

The CVD method is used to form the insulating layer 30A on theinsulating layer 29A. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 30A. By the sputter method, theconductive materials (e.g., the metal films such as Ta) with which thewiring trenches are completely filled are formed in a thickness of about50 nm on the insulating layer 30A. Thereafter, by the CMP, theconductive materials are polished, and the local interconnect line(lower electrode of the MTJ element) 22 is formed.

The CVD method is used to successively deposit a plurality of layers onthe local interconnect line 22, and these plurality of layers arefurther patterned to form the MTJ elements 23.

The CVD method is used to form the insulating layer 30B with which theMTJ element 23 is coated, and subsequently, the insulating layer 30B onthe MTJ element 23 is removed, for example, by the CMP method. As aresult, the topmost layer of the MTJ element 23 is exposed, and only theside surfaces of the MTJ element 23 are coated with the insulating layer30B.

It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

Subsequently, as shown in FIG. 23, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

Furthermore, the yoke material (such as NiFe) 26 which has the highpermeability is continuously formed in a thickness of about 50 nm on thebarrier layer 30 by the sputter method. Thereafter, the PEP method isused to form the resist pattern 33.

Additionally, the RIE method is used, and the resist pattern 33 is usedas the mask to etch the yoke material 26, barrier layer 30, conductivematerial, and barrier metal 29, so that the data selection line(read/write bit line) 24 is formed.

Thereafter, the resist pattern 33 is removed.

Subsequently, as shown in FIG. 24, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

Moreover, when the yoke material 32 and barrier layer 31 are etched bythe RIE method, as shown in FIG. 25, the yoke material 32 and barrierlayer 31 remain only on the side wall portions of the data selectionline 24.

Furthermore, as shown in FIG. 25, the CVD method is used to form thebarrier layer (such as SiN) with which the yoke materials 26, 32 arecoated in a thickness of about 20 nm.

The magnetic random access memory of the second embodiment (FIGS. 18 and19) is completed by the above-described steps.

(3) Conclusion

As described above, according to the second embodiment, the yokematerials 25A1, 25A2, 25B1, 25B2 with which the lower and side surfacesof the intermediate layer 20A and write word line 20B are coated arefurther coated with the barrier layer 34 which has the function ofpreventing the diffusion of atoms. Moreover, the yoke materials 26, 32with which the upper and side surfaces of the data selection line 24 arecoated are further coated with the barrier layer 35 which has thefunction of preventing the diffusion of atoms.

Therefore, the atoms of the materials constituting the yoke materials25A1, 25A2, 25B1, 25B2, 26, 32 can be inhibited from being diffused inthe semiconductor substrate 11, and the characteristics of the MOStransistor can be prevented from being deteriorated.

5. THIRD EMBODIMENT

FIGS. 26 and 27 show the device structure of the magnetic random accessmemory according to a third embodiment of the present invention. It isto be noted that FIG. 26 shows the section of the Y-direction, and FIG.27 shows the section of the X-direction of the MTJ element portion ofFIG. 26. The X-direction crosses at right angles to the Y-direction.

The device structure of the present embodiment is characterized in thathard masks (such as SiO₂) are formed as masks at a wiring processingtime right on the write word line and data selection line.

The element separation insulating layers 12 including the STI structureare formed in the semiconductor substrate (such as the p-type siliconsubstrate and p-type well region) 11. The region surrounded with theelement separation insulating layers 12 is the element region in whichthe read selection switch is formed.

The read selection switch is constituted of the MOS transistor(n-channel type MOS transistor). The gate insulating layer 13, gateelectrode 14, and side wall insulating layers 15 are formed on thesemiconductor substrate 11. The gate electrode 14 extends in theX-direction, and functions as the read word line for selecting the readcell (MTJ element) at the read operation time.

The source region (e.g., n-type diffusion layer) 16-S and drain region(e.g., n-type diffusion layer) 16-D are formed in the semiconductorsubstrate 11. The gate electrode (read word line) 14 is disposed on thechannel region between the source region 16-S and drain region 16-D.

One of the metal layers constituting the first metal wiring layerfunctions as the intermediate layer 18A for vertically stacking aplurality of contact plugs, and another layer functions as the sourceline 18B.

The intermediate layer 18A is electrically connected to the drain region16-D of the read selection switch (MOS transistor) by the contact plug17A. The source line 18B is electrically connected to the source region16-S of the read selection switch via the contact plug 17B. The sourceline 18B extends in the X-direction, for example, similarly as the gateelectrode (read word line) 14.

One of the metal layers constituting the second metal wiring layerfunctions as the intermediate layer 20A for vertically stacking aplurality of contact plugs, and another layer functions as the writeword line 20B. The intermediate layer 20A is electrically connected tothe intermediate layer 18A by the contact plug 19. The write word line20B extends, for example, in the X-direction similarly as the gateelectrode (read word line) 14.

The lower surfaces of the intermediate layer 20A and write word line 20Bare coated with the material having the high permeability, that is, yokematerials 25A1, 25B1.

The barrier metals (e.g., Ti, TiN, or the lamination of these) 27 a, 27b are formed right under the yoke materials 25A1, 25B1, and the barriermetals (e.g., Ti, TiN, or the lamination of these) 27 c, 27 d are formedright on the barrier metals. That is, the yoke materials 25A1, 25B1 areheld between the barrier metals 27 a, 27 b, 27 c, 27 d.

Moreover, the side surfaces of the intermediate layer 20A and write wordline 20B are also coated with the materials which have highpermeability, that is, yoke materials 25A2, 25B2.

When the yoke materials 25A1, 25B1, 25A2, 25B2 are used as the tractionmaterial of the magnetic force line, the magnetic field Hy generated bythe write current flowing through the write word line 20B canefficiently be concentrated on the MTJ element 23.

The barrier layers 28 a, 28 b (e.g., Ti, TiN, or the lamination ofthese, or Ta, TaN, or the lamination of these) are formed on the sidesurfaces of the intermediate layer 20A and write word line 20B. Thebarrier layers 28 a, 28 b separate the yoke materials 25A1, 25B1 withwhich the lower surfaces of the intermediate layer 20A and write wordline 20B are coated from the yoke materials 25A2, 25B2 with which theside surfaces are coated.

The barrier layers 28 a, 28 b may have either the conductivity orinsulation property. Moreover, the barrier layers 28 a, 28 b may havethe same functions as those of the barrier metals 27 a, 27 b.

Hard masks (such as SiO₂) 36A, 36B constituting the masks at the wiringprocessing time (RIE time) are formed right on the intermediate layer20A and write word line 20B.

One of the metal layers constituting the third metal wiring layerfunctions as the lower electrode 22 of the MTJ element 23. The lowerelectrode 22 is electrically connected to the intermediate layer 20A bythe contact plug 21. The MTJ element 23 is mounted on the lowerelectrode 22. Here, the MTJ element 23 is disposed right on the writeword line 20B, and formed in the rectangular shape long in theX-direction (magnetization easy axis is the X-direction).

One of the metal layers constituting the fourth metal wiring layerfunctions as the data selection line (read/write bit line) 24. The dataselection line 24 is electrically connected to the MTJ element 23, andextends in the Y-direction.

The upper surface of the data selection line 24 is coated with thematerial having the high permeability, that is, the yoke material 26.The barrier metal (e.g., Ti, TiN, or the lamination of these) 29 isformed on the lower surface of the data selection line 24, and thebarrier layer (e.g., Ti, TiN, or the lamination of these, or Ta, TaN, orthe lamination of these) 30 is formed on the upper surface of the dataselection line.

Moreover, the side surface of the data selection line 24 is also coatedwith the material which has the high permeability, that is, the yokematerials 32.

When the yoke materials 26, 32 are used as the traction material of themagnetic force line, the magnetic field Hx generated by the writecurrent flowing through the data selection line 24 can efficiently beconcentrated on the MTJ element 23.

The barrier layers 31 (e.g., Ti, TiN, or the lamination of these, or Ta,TaN, or the lamination of these) are formed on the side surfaces of thedata selection line 24. The barrier layers 31 separate the yoke material26 with which the upper surface of the data selection line 24 is coatedfrom the yoke materials 32 with which the side surfaces of the dataselection line are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29.

A hard mask (such as SiO₂) 37 is formed as the mask at the wiringprocessing time (RIE time) right on the data selection line 24.

(2) Manufacturing Method

The manufacturing method of the magnetic random access memory accordingto the third embodiment of the present invention will next be described.

First, as shown in FIG. 28, the methods such as the PEP, CVD, and CMPmethods are used to form the element separation insulating layer 12including the STI structure in the semiconductor substrate 11.

Moreover, the MOS transistor as the read selection switch is formed inthe element region surrounded with the element separation insulatinglayer 12.

After forming the gate insulating layer 13 and gate electrode (read wordline) 14 by the CVD, PEP, and RIE methods, the source region 16-S anddrain region 16-D are formed by the ion implantation method, so that theMOS transistor can easily be formed. The side wall insulating layers 15may also be formed on side wall portions of the gate electrode 14 by theCVD and RIE methods.

Thereafter, the insulating layer 28A with which the MOS transistor iscompletely coated is formed by the CVD method. Moreover, the surface ofthe insulating layer 28A is flatted using the CMP method. The contactholes reaching the source region 16-S and drain region 16-D of the MOStransistor are formed in the insulating layer 28A using the PEP and RIEmethods.

The barrier metals (e.g., Ti, TiN, or the lamination of these) 51 areformed on the insulating layer 28A and on the inner surfaces of thecontact holes by the sputter method. Continuously, the conductivematerials (e.g., the conductive polysilicon film including theimpurities, metal film, and the like) with which the contact holes arecompletely filled are formed on the insulating layer 28A by the sputtermethod. Moreover, by the CMP method, the conductive materials andbarrier metals 51 are polished, and the contact plugs 17A, 17B areformed.

The insulating layer 28B is formed on the insulating layer 28A using theCVD method. The PEP and RIE methods are used to form the wiring trenchesin the insulating layer 28B. The sputter method is used to form thebarrier metals (e.g., Ti, TiN, or the lamination of these) 52 on theinsulating layer 28B and on the inner surfaces of the wiring trenches.Continuously, the conductive materials (e.g., the metal films such asaluminum and copper) with which the wiring trenches are completelyfilled are formed on the insulating layer 28B by the sputter method.Thereafter, by the CMP, the conductive materials and barrier metals 52are polished, and the intermediate layer 18A and source line 18B areformed.

Subsequently, the CVD method is used to form the insulating layer 28C onthe insulating layer 28B. The PEP and RIE methods are used to form thevia holes in the insulating layer 28C. By the sputter method, thebarrier metals (e.g., Ti, TiN, or the lamination of these) 53 are formedon the insulating layer 28C and on the inner surfaces of the via holes.Continuously, by the sputter method, the conductive materials (e.g., themetal films such as aluminum and copper) with which the via holes arecompletely filled are formed on the insulating layer 28C. Thereafter, bythe CMP method, the conductive materials and barrier metals 53 arepolished, and the via plug 19 is formed.

Subsequently, as shown in FIG. 29, by the sputter method, the barriermetals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27 a, 27 bare formed on the insulating layer 28C. Subsequently, the sputter methodis used to form the yoke materials (e.g., NiFe) 25A1, 25B1 which havethe high permeability in a thickness of about 50 nm on the barriermetals 27 a, 27 b. Moreover, the sputter method is used to form thebarrier metals (e.g., the lamination of Ti (10 nm) and TiN (10 nm)) 27c, 27 d on the yoke materials 25A1, 25B1.

Furthermore, the sputter method is continuously used to form theconductive material (e.g., AlCu) in a thickness of about 250 nm on thebarrier metals 27 c, 27 d. Moreover, the sputter method is used to forminsulating layers (such as SiO₂) 36A, 36B as the hard masks in athickness of about 100 nm on the conductive material.

Thereafter, the resist pattern is formed by the PEP method. Moreover,the resist pattern is used as the mask to pattern the insulating layers36A, 36B as the hard masks by the RIE method. Thereafter, the resistpattern is removed.

Subsequently, this time the insulating layers 36A, 36B are used as themasks to successively etch the conductive materials, yoke materials25A1, 25B1, and barrier metals 27 a, 27 b, 27 c, 27 d by the RIE method,so that the intermediate layer 20A and write word line 20B are formed.

Additionally, the sputter method is used to form the barrier layers(e.g., the lamination of Ta (10 nm) and TaN (10 nm)) 28 a, 28 b withwhich the intermediate layer 20A and write word line 20B are coated. Thesputter method is continuously used to form the yoke materials (e.g.,NiFe) 25A2, 25B2 which have the high permeability in a thickness ofabout 50 nm on the barrier layers 28 a, 28 b.

Moreover, by the RIE method, the yoke materials 25A2, 25B2 and barrierlayers 28 a, 28 b are etched, so that the yoke materials 25A2, 25B2 andbarrier layers 28 a, 28 b remain only on the side wall portions of theintermediate layer 20A and write word line 20B.

Thereafter, the CVD method is used to form the insulating layer 29A withwhich the intermediate layer 20A and write word line 20B are completelycoated on the barrier layer 34. Moreover, for example, by the CMPmethod, the surface of the insulating layer 29A is flatted.

Subsequently, as shown in FIG. 30, the PEP and RIE methods are used toform the via holes which reach the intermediate layer 20A in theinsulating layer 29A. By the sputter method, the barrier metals (e.g.,Ti, TiN, or the lamination of these) 55 are formed on the insulatinglayer 29A and on the inner surfaces of the via holes in a thickness ofabout 10 nm. Continuously, the conductive materials (e.g., the metalfilm such as tungsten) with which the via holes are completely filledare formed on the insulating layer 29A by the CVD method. Thereafter, bythe CMP method, the conductive materials and barrier metals 55 arepolished, and the via plug 21 is formed.

The CVD method is used to form the insulating layer 30A on theinsulating layer 29A. The PEP and RIE methods are used to form thewiring trenches in the insulating layer 30A. By the sputter method, theconductive materials (e.g., the metal films such as Ta) with which thewiring trenches are completely filled are formed in a thickness of about50 nm on the insulating layer 30A. Thereafter, by the CMP, theconductive materials are polished, and the local interconnect line(lower electrode of the MTJ element) 22 is formed.

The CVD method is used to successively deposit a plurality of layers onthe local interconnect line 22, and these plurality of layers arefurther patterned to form the MTJ elements 23.

The CVD method is used to form the insulating layer 30B with which theMTJ element 23 is coated, and subsequently, the insulating layer 30B onthe MTJ element 23 is removed, for example, by the CMP method. As aresult, the topmost layer of the MTJ element 23 is exposed, and only theside surfaces of the MTJ element 23 are coated with the insulating layer30B.

It is to be noted that to constitute the topmost layer of the MTJelement 23 by Ta or W, the topmost layer of the MTJ element 23 isexposed, and subsequently the data selection line described later candirectly be formed.

Subsequently, as shown in FIG. 31, the barrier metal (e.g., thelamination of Ti (10 nm) and TiN (10 nm)) 29 is formed on the insulatinglayer 30B by the sputter method. Continuously, the conductive material(such as AlCu) is formed in a thickness of about 400 nm on the barriermetal 29 by the sputter method. Continuously, the barrier layer (e.g.,the lamination of Ta (10 nm) and TaN (10 nm)) 30 is formed on theconductive material by the sputter method.

Furthermore, the yoke material (such as NiFe) 26 which has the highpermeability is continuously formed in a thickness of about 50 nm on thebarrier layer 30 by the sputter method. Moreover, the insulating layer(such as SiO₂) 37 which functions as the hard mask at the wiringprocessing time is formed on the yoke material 26 by the sputter method.Thereafter, the PEP method is used to form the resist pattern 33.

Additionally, the resist pattern 33 is used as the mask to pattern theinsulating layer 37 as the hard mask by the RIE method. Thereafter, theresist pattern 33 is removed.

Subsequently, as shown in FIG. 32, this time the insulating layer 37 isused as the mask to successively etch the yoke material 26, barrierlayer 30, conductive material, and barrier metal 29 by the RIE method,so that the data selection line (read/write bit line) 24 is formed.

Subsequently, as shown in FIG. 33, the barrier layer (e.g., thelamination of Ta (10 nm) and TaN (10 nm)) 31 with which the dataselection line 24 is coated is formed on the insulating layer 30B by thesputter method. Continuously, the yoke material (such as NiFe) 32 whichhas the high permeability is formed in a thickness of about 50 nm on thebarrier layer 31 by the sputter method.

Moreover, when the yoke material 32 and barrier layer 31 are etched bythe RIE method, as shown in FIG. 34, the yoke material 32 and barrierlayer 31 remain only on the side wall portions of the data selectionline 24.

The magnetic random access memory of the third embodiment (FIGS. 26 and27) is completed by the above-described steps.

(3) Conclusion

As described above, according to the third embodiment, to process theintermediate layer 20A and write word line 20B, the hard mask (such asSiO₂) is used as the mask of RIE, not a photoresist. Therefore, at theRIE time, an etching selection ratio can sufficiently be secured betweenthe mask material, and the conductive material, yoke material, andbarrier metal.

Similarly, also to process the data selection line 24, not thephotoresist, but the hard mask (such as SiO₂) is used as the mask ofRIE. Therefore, at the RIE time, the etching selection ratio cansufficiently be secured between the mask material, and the yokematerial, barrier layer, conductive material, and barrier metal.

6. FOURTH EMBODIMENT

FIGS. 35 and 36 show the device structure of the magnetic random accessmemory according to a fourth embodiment of the present invention. It isto be noted that FIG. 35 shows the section of the Y-direction, and FIG.36 shows the section of the X-direction of the MTJ element portion ofFIG. 35. The X-direction crosses at right angles to the Y-direction.

The device structure of the present embodiment is characterized in thatthe yoke materials 25A1, 25A2, 25B1, 25B2 are constituted of conductivematerials, and the yoke materials 26, 32 and barrier layers 28 a, 28 b,30, 31 are constituted of insulating materials in the device of thefirst embodiment.

That is, the yoke materials 25A1, 25A2, 25B1, 25B2, 26, 32 and barrierlayers 28 a, 28 b, 30, 31 may also be constituted of the conductive orinsulating materials.

7. FIFTH EMBODIMENT

FIG. 37 shows the device structure of the magnetic random access memoryaccording to a fifth embodiment of the present invention.

The device structure of the present embodiment is characterized in thatthe structure of a write line in the first embodiment is applied to themagnetic random access memory having a so-called ladder type cell arraystructure.

In the ladder type cell array structure, a plurality of (four in thepresent embodiment) MTJ elements 23 are arranged in a lateral direction(direction parallel to the surface of the semiconductor substrate) onthe semiconductor substrate 11. These MTJ elements 23 are connected inparallel between the data selection line (read/write bit line) 24 andlower electrode.

One end of the MTJ element 23 is directly connected to the dataselection line 24, and the other end of the element is connected incommon to a read selection switch RSW via the lower electrode. Aplurality of MTJ elements 23 share one data selection line 24.

The data selection line 24 is disposed right on the plurality of MTJelements 23, and extends in the Y-direction. The upper surface of thedata selection line 24 is coated with the yoke material 26 having thehigh permeability, and the side surfaces of the line are coated with theyoke materials 32 having the high permeability.

The barrier layer 30 is disposed between the data selection line 24 andyoke material 26, and the barrier layer 31 is disposed between the dataselection line 24 and yoke material 32. The barrier layer 31 separatesthe yoke material 26 with which the upper surface of the data selectionline 24 is coated from the yoke materials 32 with which the sidesurfaces of the data selection line 24 are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29.

The write word line 20B is disposed right under the MTJ element 23, andextends in the X-direction crossing at right angles to the Y-direction.The lower surface of the write word line 20B is coated with the yokematerial 25B1 having the high permeability, and the side surfaces of theline are coated with the yoke material 25B2 having the highpermeability.

The barrier layer 28 b is disposed between the write word line 20B andyoke material 25B2. The barrier layer 28 b separates the yoke material25B1 with which the lower surface of the write word line 20B is coatedfrom the yoke materials 25B2 with which the side surfaces of the writeword line 20B are coated.

The barrier layer 28 b may have either the conductivity or insulationproperty. Moreover, the barrier layer 28 b may have the same function asthat of the barrier metal 27 b.

It is to be noted that in the fifth embodiment the yoke materials 25B1,25B2, 26, 32, barrier metals 27 b, 27 d, and barrier layers 28 b, 30, 31may also be constituted of the conductive or insulating materials.

8. SIXTH EMBODIMENT

FIG. 38 shows the device structure of the magnetic random access memoryaccording to a sixth embodiment of the present invention.

The device structure of the present embodiment is characterized in thatthe structure of the write line in the first embodiment is applied tothe magnetic random access memory having another type of cell arraystructure.

In the cell array structure, a plurality of (four in the presentembodiment) MTJ elements 23 are arranged in the Y-direction (directionparallel to the surface of the semiconductor substrate) on thesemiconductor substrate 11. These MTJ elements 23 are connected betweenthe write word line 20B extending in the X-direction and the upperelectrode.

One end of the MTJ element 23 is directly connected to the write wordline 20B, and the other end of the element is connected in common to theread selection switch RSW via the upper electrode. A plurality of MTJelements 23 share one data selection line 24.

The data selection line 24 is disposed right on the plurality of MTJelements 23, and extends in the Y-direction. The upper surface of thedata selection line 24 is coated with the yoke material 26 having thehigh permeability, and the side surfaces of the line are coated with theyoke materials 32 having the high permeability.

The barrier layer 30 is disposed between the data selection line 24 andyoke material 26, and the barrier layer 31 is disposed between the dataselection line 24 and yoke material 32. The barrier layer 31 separatesthe yoke material 26 with which the upper surface of the data selectionline 24 is coated from the yoke materials 32 with which the sidesurfaces of the data selection line 24 are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29.

The write word line 20B is disposed right under the MTJ element 23. Thelower surface of the write word line 20B is coated with the yokematerial 25B1 having the high permeability, and the side surfaces of theline are coated with the yoke material 25B2.

The barrier layer 28 b is disposed between the write word line 20B andyoke material 25B2. The barrier layer 28 b separates the yoke material25B1 with which the lower surface of the write word line 20B is coatedfrom the yoke materials 25B2 with which the side surfaces of the writeword line 20B are coated.

The barrier layer 28 b may have either the conductivity or insulationproperty. Moreover, the barrier layer 28 b may have the same function asthat of the barrier metal 27 b.

It is to be noted that in the sixth embodiment the yoke materials 25B1,25B2, 26, 32, barrier metals 27 b, 27 d, 29 and barrier layers 28 b, 30,31 may also be constituted of the conductive or insulating materials.

9. SEVENTH EMBODIMENT

FIG. 39 shows the device structure of the magnetic random access memoryaccording to a seventh embodiment of the present invention.

The device structure of the present embodiment is characterized in thatthe structure of the write line in the first embodiment is applied tothe magnetic random access memory having a so-called cross point typecell array structure.

In the cross point type cell array structure, a plurality of (four inthe present embodiment) MTJ elements 23 are arranged in the Y lateraldirection (direction parallel to the surface of the semiconductorsubstrate) on the semiconductor substrate 11. These MTJ elements 23 areconnected between the data selection line (read/write bit line) 24extending in the Y-direction and the write word line 20B extending inthe X-direction intersecting with the Y-direction.

One end of the MTJ element 23 is directly connected to the dataselection line 24, and the other end of the element is directlyconnected to the write word line 20B.

The data selection line 24 is disposed right on the plurality of MTJelements 23. The upper surface of the data selection line 24 is coatedwith the yoke material 26 having the high permeability, and the sidesurfaces of the line are coated with the yoke materials 32 having thehigh permeability.

The barrier layer 30 is disposed between the data selection line 24 andyoke material 26, and the barrier layer 31 is disposed between the dataselection line 24 and yoke material 32. The barrier layer 31 separatesthe yoke material 26 with which the upper surface of the data selectionline 24 is coated from the yoke materials 32 with which the sidesurfaces of the data selection line 24 are coated.

The barrier layers 30, 31 may have either the conductivity or insulationproperty. Moreover, the barrier layers 30, 31 may have the samefunctions as those of the barrier metal 29.

The write word line 20B is disposed right under the MTJ element 23. Thelower surface of the write word line 20B is coated with the yokematerial 25B1 having the high permeability, and the side surfaces of theline are coated with the yoke material 25B2 having the highpermeability.

The barrier layer 28 b is disposed between the write word line 20B andyoke material 25B2. The barrier layer 28 b separates the yoke material25B1 with which the lower surface of the write word line 20B is coatedfrom the yoke materials 25B2 with which the side surfaces of the writeword line 20B are coated.

The barrier layer 28 b may have either the conductivity or insulationproperty. Moreover, the barrier layer 28 b may have the same function asthat of the barrier metal 27 b.

It is to be noted that in the seventh embodiment the yoke materials25B1, 25B2, 26, 32, barrier metals 27 b, 27 d, and barrier layers 28 b,30, 31 may also be constituted of the conductive or insulatingmaterials.

10. Others

In the description of the first, second reference examples, first toseventh embodiments, and manufacturing method, the present invention hasbeen described in terms of the examples of the cell array structure inwhich the memory cell is constituted of one MTJ element and one readselection switch, ladder type cell array structure, and cross point typecell array structure.

However, the present invention is not limited to the magnetic randomaccess memory of the cell array structure, and can be applied to all themagnetic random access memories including the device structures shown inthe first, second reference examples and first to seventh embodiments.

Moreover, the yoke materials on the upper or lower surface of the writeline may be separated from the yoke materials on the side surfaces ofthe write line by the barrier layer. With the yoke material, all or someof the surfaces of the write line excluding the surface on the MTJelement side may also be coated.

As described above, according to the magnetic random access memory ofthe embodiment of the present invention, since the yoke material on theupper or lower surface of the write line is separated from the yokematerial on the side surface by the barrier layer, the film thicknessand magnetic domain of the yoke material can easily be controlled. Atthe write operation time, the synthetic magnetic field can efficientlybe exerted to the MTJ element.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventionconcept as defined by the appended claims and their equivalents.

1. A magnetic random access memory comprising: a memory cell which usesa magneto resistive effect; a write line which flows a current forwriting data to the memory cell unit, said write line having a firstsurface and a second surface adjacent to the first surface; a first yokematerial which coats the first surface of the write line; and a secondyoke material which coats the second surface of the write line; and abarrier layer which separates the first yoke material from the secondyoke material, wherein the second surface of the write line is a sidesurface of the write line and the barrier layer is continuously providedfrom a portion between the first yoke material and the second yokematerial to a portion under the second yoke material.
 2. The magneticrandom access memory according to claim 1, wherein the memory cell unitcomprises a magneto resistive element and a read selection switchconnected to the magneto resistive element.
 3. The magnetic randomaccess memory according to claim 2, wherein the read switch is one of aMOS transistor and a diode.
 4. The magnetic random access memoryaccording to claim 1, wherein the memory cell unit comprises a pluralityof magneto resistive elements and a read selection switch connected tothe magneto resistive elements.
 5. The magnetic random access memoryaccording to claim 4, wherein the read selection switch is one of a MOStransistor and a diode.
 6. The magnetic random access memory accordingto claim 1, wherein the memory cell unit comprises a plurality ofmagneto resistive elements connected in parallel and a read selectionswitch connected to the magneto resistive elements, and the magneticrandom access memory is a ladder type.
 7. The magnetic random accessmemory according to claim 6, wherein the read selection switch is one ofa MOS transistor and a diode.
 8. The magnetic random access memoryaccording to claim 1, wherein the memory cell unit comprises a magnetoresistive element connected to the write line, and the magnetic randomaccess memory is a cross point type.
 9. A magnetic random access memoryaccording to claim 1, wherein the barrier layer is disposed between thefirst yoke material and the write line and between the second yokematerial and the write line.
 10. A magnetic random access memoryaccording to claim 1, wherein the barrier layer sandwiches the first andsecond yoke materials.
 11. A magnetic random access memory according toclaim 1, wherein the barrier layer is constituted of a conductivematerial.
 12. A magnetic random access memory according to claim 1,wherein the barrier layer comprises an insulating material.
 13. Amagnetic random access memory according to claim 1, wherein the barrierlayer has a function of preventing diffusion of atoms constituting thefirst and second yoke materials.
 14. A magnetic random access memoryaccording to claim 1, wherein the barrier layer comprises a metalincluding one of Ti and Ta.
 15. A magnetic random access memoryaccording to claim 1, wherein the barrier layer comprises SiN.
 16. Amagnetic random access memory according to claim 1, wherein the barrierlayer has a thickness of at least 20 nm.
 17. A magnetic random accessmemory according to claim 1, wherein the first surface is an uppersurface of the write line.
 18. A magnetic random access memory accordingto claim 1, wherein the first surface is a lower surface of the writeline.
 19. A magnetic random access memory according to claim 1, whereinthe write line has a function of reading data from the memory cell unit.20. A magnetic random access memory according to claim 1, furthercomprising an intermediate layer having a same structure as that of thewrite line.